<<<Since the input Z of most solid-state amps is well-controlled at 50-ohms, that the input Z should not appreciably change as output Z changes, then can't we simply use a feed-forward ALC system instead of feedback ALC? A fast RF voltage peak detector can be bridged across the amp's input Z. When the RF voltage exceeds ~ 70.7Vpk, correction bias is applied to the solid-state PA. Simultaneously, a 3dB pad could then be inserted at the amp input until average input power drops below 50W. >>>
We can protect the amp if we can change bias or switch a pad a lot faster than the rise time of the envelope, but that does not help the bandwidth. It could actually make the bandwidth problem worse, and is unlikely to make it better. The ideal solution would be to have a system that remembers the ALC required, and starts the transmitter with just a bit less than the expected voltage and makes slow or small adjustments or corrections from there. Better yet, why are most radios made the way they are? Put the SSB ALC entirely in the audio system. For example we could split-frequency process the audio with far more effective results and less intermodulation or harmonic distortion than any type of RF clipping or compression. The VOMAX did that, although not nearly as well as we could do with a DSP system, in the 70's or 80's. We should be doing all the gain control and processing at audio. Trying to fix transmitter issues at the amplifier by wrapping the amp back into the transmitter controls just doesn't seem logical. RF clipping or limiting, unless it is gain reduction with a PIN diode attenuator, doesn't make much sense to me. 73 Tom ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
